Previous approaches to addressing sensing needs have generally involved using a single light signal from a light source, such as a light emitting diode, and multiple detectors. In order to illuminate a large area in an environment using a single light source, two general methods are known. One approach typically involves emitting a broad light signal from the light source and detecting the signal with one of multiple detectors positioned throughout the environment. The other approach typically involves emitting a narrow light signal from the light source, spreading the signal around the environment by reflecting it off of a rotating mirror, for instance, and detecting the signal with one of multiple detectors positioned throughout the environment. While feasible, both approaches typically require multiple detectors and are usually not power efficient as a result, yielding a low signal-to-noise ratio. A poor power-transfer ratio reflects this inefficiency as the individual detector that receives a light signal usually detects only a portion of the signal that was originally emitted. Consequently, the signal that was detected generally provides only limited information about an object being sensed in the environment. These approaches also tend to limit the size range of the object being sensed in an environment due to the nature of the single light signal.
The limitations of these previous approaches are often manifested in applications such as detecting the motion of an object in an environment. Many motion detection systems generally involve a line-of-sight operation, where at least one detector detects the motion of an object as the object breaks a beam of light emitted from a light source. In relatively simple applications, such as determining the presence or absence of an object, this approach generally suffices. For more complex applications, such as determining the direction of the object's motion, this approach proves less adequate. When an object moves across a single light signal emitted by a light source, the signal received by a detector gradually decreases as the signal blocked by the object gradually increases. This gradual change in signal detection typically requires a complex algorithm to determine the position of the object in the environment. Adding multiple detectors can provide more information and decrease the complexity of the algorithm required, though this introduces power inefficiencies as mentioned previously, as well as adding costs associated with additional hardware.
The limitations of the aforementioned approaches also relate to applications involving object recognition. Many known systems, either for recognizing only specific objects or for mapping spatial characteristics of objects, involve spreading a light signal with a rotating mirror and/or using multiple detectors. Holograms can also be used to spread the light signal by dividing the signal into smaller light signals. An approach for detecting only specific objects involves emitting pulses of signals from a transceiver, receiving the signals that reflect off of an object, and comparing the received signals with preset signals reflected off of known objects. Information about the known objects is typically stored in a database. An approach for mapping an object involves superimposing light signals received by different detectors in the presence of an object and comparing the signals with respect to signals associated with the environment without the object.
While each of these approaches is feasible for a particular function, none is known to perform several functions. This deficit creates a need for a versatile system that is both power efficient and cost effective. Such a system could be capable of, for instance, detecting the presence or absence of any object or of a specific object, detecting the spatial characteristics of an object, detecting the motion of any object or a specific object, or detecting various characteristics about the motion of an object.